Infrared absorption spectra of electronically excited long-lived metastable states in Na-2[Ru(CN)(5)NO]center dot 2H(2)O

[Ru(CN)(5)NO](2-) can be excited selectively by two very long-lived electronic metastable states (MSI and MSII) by irradiation at low temperature with blue-near UV light. Upon excitation to MSI and MSII states, CN and NO modes suffer frequency down-shifts, a fact which implies softening of the named bonds. Shifts of vibrational modes of the RuNO group are far larger than shifts of CN modes, a fact that indicates that the metastable states involve electronic transitions mainly located at that group. The MSI and MSII states decay when heating at two different onset temperatures T-I < T-II. A thermally driven MSI-to-MSII excitation transfer process taking place in the temperature range T-II > T > T-I shows that MSII is energetically below MSI. Copyright (C) 1997 Elsevier Science Ltd